1. Field of the Invention
The invention described herein relates to articles of manufacture and to methods of fabrication of miniature multi-layer electronic devices and is more particularly concerned with the preparation of layered configurations for the formation of subminiature electrical conductors between spaced-apart conductive layers of such devices.
2. Description of the Prior Art
Conventional methods generally practiced in the art for fabricating subminiature diameter holes in thin insulating films are generally based upon etching such holes through a photoresist mask; however, the utility of conventional photoresist techniques for the purpose is generally limited to dimensions of one micron or greater. Electron beam lithographic techniques offer the possibility of producing masks for generating small holes; however, if chemical (wet) etching is used with such a mask, severe undercutting of the material just below the mask results and there is no fully effective control over the diametric dimension of the bore. If conventional plasma or ion milling etching (dry etching) methods are employed, minimal undercutting is desirably achieved, but typical resist materials are rapidly destroyed when exposed to the reactive gas environments typical of these lattter two methods, so that an acceptable product is not reliably generated and is correspondingly expensive. While multiple weak link superconductor devices have been successfully made using standard electron resist techniques to pattern and to etch micron holes in a silicon dioxide layer, there has been demonstrated a need for a more reliable method for generating such holes and submicron conductors passing therethrough in superconductive devices such as described by Harry Kroger in the U.S. patent application Ser. No. 836,452 for a "Multiple Weak Link Squid", filed Sept. 26, 1977, now abandoned, and assigned to Sperry Rand Corporation. A reliable, easily repeatable, and inexpensive process is desired, since the superconductor devices involved have wide possibilities for competitive use in commercial signal processors and computers.